This invention pertains to semiconductor capacitor constructions and to methods of forming semiconductor capacitor constructions. The invention is thought to have particular significance in application to methods of forming dynamic random access memory (DRAM) cell structures, and to DRAM cell structures.
A commonly used semiconductor memory device is a DRAM cell. A DRAM cell generally consists of a capacitor coupled through a transistor to a bitline. A continuous challenge in the semiconductor industry is to increase DRAM circuit density. Accordingly, there is a continuous effort to decrease the size of memory cell components. A limitation on the minimal size of cell components is impacted by the resolution of a photolithographic etch during a fabrication process. Although this resolution is generally being improved, at any given time there is a minimum photolithographic feature dimension of which a fabrication process is capable. It would be desirable to form DRAM components having at least some portions which comprise a cross-sectional dimension of less than a given minimum capable photolithographic feature dimension.
Another continuous trend in the semiconductor industry is to minimize processing steps. Accordingly, it is desirable to utilize common steps for the formation of separate DRAM components. For instance, it is desirable to utilize common steps for the formation of the DRAM capacitor structures and the DRAM bitline contacts.
A semiconductor wafer fragment 10 is illustrated in FIG. 1 showing a prior art DRAM array 83. Wafer fragment 10 comprises a semiconductive material 12, field oxide regions 14, and wordlines 24 and 26. Wordlines 24 and 26 comprise a gate oxide layer 16, a polysilicon layer 18, a silicide layer 20 and a silicon oxide layer 22. Silicide layer 20 comprises a refractory metal silicide, such as tungsten silicide, and polysilicon layer 18 typically comprises polysilicon doped with a conductivity enhancing dopant. Nitride spacers 30 are laterally adjacent wordlines 24 and 26.
Electrical node locations 25, 27 and 29 are between wordlines 24 and 26 and are electrically connected by transistor gates comprised by wordlines 24 and 26. Node locations 25, 27 and 29 are diffusion regions formed within semiconductive material 12.
A borophosphosilicate glass (BPSG) layer 34 is over semiconductive material 12 and wordlines 24 and 26. An oxide layer 32 is provided between BPSG layer 34 and material 12. Oxide layer 32 inhibits diffusion of phosphorus from BPSG layer 34 into underlying materials.
Conductive pedestals 54, 55 and 56 extend through BPSG layer 34 to node locations 25, 27 and 29, respectively. Capacitor constructions 62 and 64 contact upper surfaces of pedestals 54 and 56, respectively. Capacitor constructions 62 and 64 comprise a storage node layer 66, a dielectric layer 68, and a cell plate layer 70. Dielectric layer 68 comprises an electrically insulative layer, such as silicon nitride. Cell plate layer 70 comprises conductively doped polysilicon, and may alternatively be referred to as a cell layer 70. Storage node layer 66 comprises conductively doped hemispherical grain polysilicon.
A conductive bitline plug 75 contacts an upper surface of pedestal 55. Bitline plug 75 may comprise, for example, tungsten. Together, bitline plug 75 and pedestal 55 comprise a bitline contact 77.
A bitline 76 extends over capacitors 62 and 64 and in electrical connection with bitline contact 77. Bitline 76 may comprise, for example, aluminum.
The capacitors 62 and 64 are electrically connected to bitline contact 77 through transistor gates comprised by wordlines 26. A first DRAM cell 79 comprises capacitor 62 electrically connected to bitline 76 through a wordline 26 and bitline contact 77. A second DRAM cell 81 comprises capacitor 64 electrically connected to bitline 76 through wordline a 26 and bitline contact 77. DRAM array 83 comprises first and second DRAM cells 79 and 81.
The invention includes a number of methods and structures pertaining to semiconductor circuit technology, including: methods of forming DRAM memory cell constructions; methods of forming capacitor constructions; methods of forming capacitor and bitline constructions; DRAM memory cell constructions; capacitor constructions; capacitor and bitline constructions, and integrated circuitry.
The invention encompasses a method of forming a capacitor wherein a first layer is formed over a node location and a semiconductive material masking layer is formed over the first layer, wherein an opening is etched through the semiconductive material masking layer and first layer to the node location using the semiconductive material masking layer as an etch mask, wherein a storage node layer is formed within the opening and in electrical connection with the masking layer, and wherein at least the masking layer is patterned to form a capacitor storage node comprising the masking layer and the storage node layer.
The invention also encompasses a method of forming a capacitor wherein a first layer is formed over a node location, wherein a semiconductive material masking layer is formed over the first layer, wherein an opening is etched through the semiconductive material masking layer and first layer to the node location using the semiconductive material masking layer as an etch mask, wherein a storage node layer is formed to substantially fill the opening and in electrical connection with the masking layer, and wherein the masking layer and the storage node layer are patterned to form a capacitor storage node.
The invention also encompasses a DRAM cell comprising a capacitor electrically connected to a bitline through a transistor gate, wherein the capacitor comprises a storage node which, in lateral cross-section, has an outer surface extending over its top, along a pair of its opposing lateral surfaces, and within laterally opposing cavities beneath it. The capacitor further comprises a dielectric layer against the storage node outer surface and extending along the lateral opposing surfaces of the storage node and within the opposing cavities beneath the storage node. Additionally, the capacitor comprises a cell plate layer against the dielectric layer and extending along the lateral opposing surfaces of the storage node and within the opposing cavities beneath the storage node.